In the author's opinion, there are ______ kinds of words that compose the whole vocabulary.

A．They are words we become acquainted in ordinary conversation.
B．They are those words we learn from the members of our own family.
C．They are those words that are the exclusive possession of a limited class.
D．They are those words that concern the common things of lif

A．he is the first man to make such discoveries
B．they are the oldest artistic record ever found
C．they are much older than those found in Europe
D．the aboriginals occupied Australia for the first time